The present invention relates generally to a system and method for fixation of a spinous process. More particularly, this invention pertains to stabilization of the human spine by applying a system and method to the applicable vertebrae of the spinal column.
Systems for spinal fixation and stabilization are well established in a wide variety of embodiments. Examples in which such systems are generally used to apply force to the spinal column include correcting degenerative conditions or deformities, maintaining a proper structural environment in the healing process from traumatic surgery, or providing temporary but secure positioning of the spine to facilitate the implanting of further components for performing the same functions. Where invasive surgery has been performed, the systems are generally intended to reliably maintain such fixation of the treated spinal process post-operatively so that bony fusion of the vertebrae or other equivalent functions may be achieved.
Early systems performing these functions comprised spinous process wiring. These systems were adequate in preventing flexion but led to relatively poor fixation, particularly in the cervical region of the vertebral column, because they still permitted rotation or extension of the affected region to some extent. This mechanical deficiency is particularly apparent in patients having osteoporosis, as one prominent example.
Other fixation systems have been anchored to a portion of the spinal process using lateral bone mass screws. These systems simply screw components directly into the bone to increase stability. Plates or rods may be utilized to fuse adjacent segments of the spine. However, there are additional problems associated with this method. The bone of the spinous process may be too soft to maintain immobility of the process over time and with increased activity. The method carries some attendant risk of major complications such as vertebral artery or root nerve injury. Further, lateral mass screw fixation systems are technically demanding and therefore may be quite inconvenient to implant and/or to remove.
More recently, systems have been developed to compress portions of the spinous process by sandwiching the processes between a plurality of plates. These plates are tightened with screws that extend through the plates and may or may not contact the spinous process itself, as desired or necessary under the circumstances. Generally speaking, these processes have improved stability without most of the limitations or inconveniences of the previous systems. However, these systems remain troublesome or inadequate where circumstances require fusion of spinous processes having a variety of dimensions, such as where the affected regions range across multiple bodies of vertebrae. Where subjects of variable sizes are involved such as large adults versus small children the problems may be pronounced further.
What is needed, therefore, is a modular system that may reliably perform the necessary function of stabilizing a portion of the spinous process, and that may flexibly adapt to processes of varying sizes and needs. The system would preferably not require any wiring or screwing in of components directly to the spinous process.
There is a further need that the system be able to stabilize multiple adjacent levels of the spinal column, while allowing for safe, quick and convenient implantation and removal of the system.